The network analyzer has established itself as an important tool in the development and production of RF and microwave equipment. It allows RF components to be almost completely characterized, which is otherwise only possible through considerable effort and by using several test instruments. Today, however, the demand for higher frequencies and data transmission rates, together with new communication technologies are placing increasing demands on test and measurement equipment. Modern network analyzers must therefore not only be fast, accurate and flexible, but also support the user in carrying out complex measurements.
With these requirements in mind, Rohde & Schwarz has developed a new generation of network analyzers. The R&S ZVB is for the medium class and available with two, three or four ports in frequency ranges up to 4, 8 and 20 GHz. The new, premium-class R&S ZVA24, which is highlighted in this article, covers the frequency range from 10 MHz up to 24 GHz and comes with either two or four ports.
This new high end network analyzer features a dynamic range of more than 130 dB, an IF bandwidth of up to 1 MHz and a measurement speed of < 3.5 ms per test point. Such a powerful instrument is thus especially suitable for demanding applications in the development of RF components, where maximum accuracy, dynamic range and sensitivity as well as flexibility are what count.
Like all of the company’s network analyzers, the R&S ZVA24 uses the tried-and-tested fundamental mixing concept, which allows the receivers to attain a high dynamic range and low trace noise even at a large measurement bandwidth. A separate generator is provided for each pair of test ports. The signals can be output at the two test ports simultaneously or in turn.
Due to the system concept, the extremely fast and independent synthesizers for the generator and receiver, and the separate reference and measurement channels of the reflectometers, the analyzer features comprehensive test capabilities and high flexibility. This is important especially for complex frequency converting and balanced measurements on active components such as amplifiers, mixers or frequency converters.
Frequency converting devices are crucial components in many RF and microwave applications, and therefore require comprehensive measurements. The instrument’s high output power and wide electronic power sweep range of more than 50 dB enables amplifiers and mixers to be characterized without additional preamplifiers — wear-free and dependent on frequency and level. The entire electronic power range of more than 50 dB can be swept quickly without interruption and without having to switch mechanical attenuators. This makes it possible to display the behavior of small and large signals within one single sweep. If a second independent source is available (as is the case with the four-port model), intermodulation measurements on amplifiers and conversion gain measurements on mixers can be performed without an additional external generator.
If the sensitivity of the receivers or the output levels of the generator do not suffice for special measurements, direct generator and receiver access is an option. The signal paths of the receivers and generators are routed to the front panel via SMA connectors, allowing the user to bypass the internal couplers and access the generators and receivers of all reflectometers directly.
With a fully configured four-port R&S ZVA24, all eight receivers can simultaneously capture and evaluate data in real time. The generator and receiver attenuators, which are available as options for each port, enable measurements to be performed at extremely small generator levels (< –100 dBm) and the maximum compression point of the receiver. The maximum generator output provides a level of typically > +15 dBm, producing a typically dynamic range of up to 145 dB for measurements via the direct receiver input.
Although the network analyzer satisfies virtually all requirements with regard to test capabilities and specifications, the intuitive operating concept enables even inexperienced users to perform and comprehensively document complex measurements quickly. The intelligent operating concept not only facilitates the solving of difficult measurement tasks quickly and easily, it can also handle a large number of traces and measurement data. The instrument can be operated via context-sensitive pull-down menus using the mouse as well as via hard keys and soft keys.
A convenient ‘Wizard’ guides the user step-by-step, using diagrams and clear selection menus, to configure the most important basic measurement settings, including calibration, if required (illustrated in Figure 1). The S-parameter wizard, for example, helps to configure a complete measurement of all 16 mixed-mode S-parameters with just a few keystrokes.
In addition, there are extensive on-line help functions that include many detailed explanations as well as the required IEC/IEEE bus commands. The Undo button can cancel a series of operating steps or simply correct wrong entries, including presets.
The virtually unlimited number of set ups can be saved on the R&S ZVA24’s integrated hard disk and called up at any time. Up to 100 set ups can be loaded in the analyzer’s RAM simultaneously, allowing users to switch from one set up to another within milliseconds by pressing a key, clicking the mouse or entering a control command.
Furthermore, up to 20,001 test points per trace can be saved, and convenient marker and analysis functions for evaluating measurement results as well as import and export possibilities for different formats are available. Traces — even from different measurement channels — can be combined as desired in individual diagrams (see Figure 2) and also linked to mathematical functions by means of the versatile formula editor. A DUT can thus be measured under a wide range of stimulus conditions, and all relevant parameters can be displayed on the screen. All traces, measurement channels and the marker can be labeled to make them clearer to distinguish. During the measurements, any existing matching network or parasitic effects can be easily included in the calculations by means of an integrated (de-)embedding function (shown in Figure 3).
Although manual calibration methods can be used for multiport measurements, they are very time-consuming, error-prone and cause relatively strong mechanical wear of the calibration standards. For the new family of network analyzers, Rohde & Schwarz therefore offers automatic calibration units for single-port and multiport calibrations (see Figure 4). Providing ports, port groups from 1 to 4 can be calibrated independently. Controlled and powered via a USB interface, and providing high temperature stability, the units are ready to operate very shortly after being connected. The calibration runs automatically, allowing, for example, a complete four-port calibration with 201 points to be completed in less than 30 seconds.
The new R&S NWA series supports not only the classic through, open, short, match (TOSM) calibration method but also a number of other calibration methods. Since each of the R&S ZVA24’s ports is equipped with its own reference receiver, adaptable and efficient seven-term calibration methods such as through/line, reflect, line (TRL/LRL), through, open, match (TOM), through, network, attenuator (TNA) and through, reflect, match (TRM) can also be used. Calibration in test fixtures or on wafers is thus possible with high measurement accuracy.
The R&S ZVA24 is an instrument that sets standards in terms of specifications, test capabilities and operating concept. It provides developers with a future-proof solution. This analyzer is particularly suitable for demanding measurement tasks in the lab and for special tasks in production. It belongs to a new generation of premium vector network analyzers that includes the medium-class R&S ZVB, outlined previously, and the R&S ZVT8 — a network analyzer for demanding production and laboratory applications up to 8 GHz, which can be fitted with up to eight integrated test ports. All models feature comprehensive functionality, high flexibility and a powerful state-of-the-art user interface. Therefore, they can easily and efficiently solve a wide range of development and production measurement tasks.
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